During the operation process of the organic light emitting diode (OLED) panel, the efficiency of the DC-DC conversion circuit that supplies power to the OLED panel refers to a ratio of the output power to the input power. The power consumption of the OLED panel may be considered as a product of the output voltage and the output current of the DC-DC conversion circuit.
At present, the DC-DC conversion circuit for powering the OLED panel generally outputs two power supply signals, that is, a boost circuit in the DC-DC conversion circuit outputs a first power supply signal VDD, and a buck-boost circuit in the DC-DC conversion circuit outputs a second power supply signal VSS. The first power supply signal VDD may have a positive voltage, and the second power supply signal VSS may have a negative voltage. The OLED panel may be supplied with a voltage difference between the first power supply signal VDD and the second power supply signal VSS, so as to enable the OLED panel to work under the driving of a driving circuit (e.g., a driver IC). When the OLED panel works normally, the voltage outputted by the DC-DC conversion circuit, i.e., the voltage difference between the first power supply signal VDD and the second power supply signal VSS, is a constant value.
Assuming that the voltage outputted by the DC-DC conversion circuit is A, the output current of the DC-DC conversion circuit will change with the variation in the load, but vary within a range [B, C] (B is smaller than C). When the load of the DC-DC conversion circuit is relatively small, the current outputted by the DC-DC conversion circuit will decrease. When the load of the DC-DC conversion circuit is relatively large, the current outputted by the DC-DC conversion circuit will increase. It can be appreciated that, in case the voltage outputted by the DC-DC conversion circuit is lower than A, the DC-DC conversion circuit may also have an output current with a value of B. When the OLED panel displays a low gray scale image, the OLED panel requires a relatively small current, in this case, the current outputted by the DC-DC conversion circuit for example may have a value of B, and the required current B may correspond to an output voltage of the DC-DC conversion circuit that is smaller than A. Hence, in such a case, if the DC-DC conversion circuit is controlled to output a current with a value of B when the voltage difference outputted by the DC-DC conversion circuit is A, too much electric energy may be consumed by the DC-DC conversion circuit is actually, thereby increasing the power consumption of the DC-DC conversion circuit and reducing the efficiency of the DC-DC conversion circuit.
To sum up, when the OLED panel works normally, the voltage outputted by the DC-DC conversion circuit may have a constant value, while the current provided by the DC-DC conversion circuit to the OLED panel will vary with the variation in load, which may result in an increased power consumption when the current outputted by the DC-DC conversion circuit to the OLED panel is relatively small, reducing the efficiency of the DC-DC conversion circuit.